550 lines
23 KiB
Plaintext
550 lines
23 KiB
Plaintext
# HEADER_CHECKS(5) HEADER_CHECKS(5)
|
|
#
|
|
# NAME
|
|
# header_checks - Postfix built-in content inspection
|
|
#
|
|
# SYNOPSIS
|
|
# header_checks = pcre:/etc/postfix/header_checks
|
|
# mime_header_checks = pcre:/etc/postfix/mime_header_checks
|
|
# nested_header_checks = pcre:/etc/postfix/nested_header_checks
|
|
# body_checks = pcre:/etc/postfix/body_checks
|
|
#
|
|
# milter_header_checks = pcre:/etc/postfix/milter_header_checks
|
|
#
|
|
# smtp_header_checks = pcre:/etc/postfix/smtp_header_checks
|
|
# smtp_mime_header_checks = pcre:/etc/postfix/smtp_mime_header_checks
|
|
# smtp_nested_header_checks = pcre:/etc/postfix/smtp_nested_header_checks
|
|
# smtp_body_checks = pcre:/etc/postfix/smtp_body_checks
|
|
#
|
|
# postmap -q "string" pcre:/etc/postfix/filename
|
|
# postmap -q - pcre:/etc/postfix/filename <inputfile
|
|
#
|
|
# DESCRIPTION
|
|
# This document describes access control on the content of
|
|
# message headers and message body lines; it is implemented
|
|
# by the Postfix cleanup(8) server before mail is queued.
|
|
# See access(5) for access control on remote SMTP client
|
|
# information.
|
|
#
|
|
# Each message header or message body line is compared
|
|
# against a list of patterns. When a match is found the
|
|
# corresponding action is executed, and the matching process
|
|
# is repeated for the next message header or message body
|
|
# line.
|
|
#
|
|
# Note: message headers are examined one logical header at a
|
|
# time, even when a message header spans multiple lines.
|
|
# Body lines are always examined one line at a time.
|
|
#
|
|
# For examples, see the EXAMPLES section at the end of this
|
|
# manual page.
|
|
#
|
|
# Postfix header or body_checks are designed to stop a flood
|
|
# of mail from worms or viruses; they do not decode attach-
|
|
# ments, and they do not unzip archives. See the documents
|
|
# referenced below in the README FILES section if you need
|
|
# more sophisticated content analysis.
|
|
#
|
|
# FILTERS WHILE RECEIVING MAIL
|
|
# Postfix implements the following four built-in content
|
|
# inspection classes while receiving mail:
|
|
#
|
|
# header_checks (default: empty)
|
|
# These are applied to initial message headers
|
|
# (except for the headers that are processed with
|
|
# mime_header_checks).
|
|
#
|
|
# mime_header_checks (default: $header_checks)
|
|
# These are applied to MIME related message headers
|
|
# only.
|
|
#
|
|
# This feature is available in Postfix 2.0 and later.
|
|
#
|
|
# nested_header_checks (default: $header_checks)
|
|
# These are applied to message headers of attached
|
|
# email messages (except for the headers that are
|
|
# processed with mime_header_checks).
|
|
#
|
|
# This feature is available in Postfix 2.0 and later.
|
|
#
|
|
# body_checks
|
|
# These are applied to all other content, including
|
|
# multi-part message boundaries.
|
|
#
|
|
# With Postfix versions before 2.0, all content after
|
|
# the initial message headers is treated as body con-
|
|
# tent.
|
|
#
|
|
# FILTERS AFTER RECEIVING MAIL
|
|
# Postfix supports a subset of the built-in content inspec-
|
|
# tion classes after the message is received:
|
|
#
|
|
# milter_header_checks (default: empty)
|
|
# These are applied to headers that are added with
|
|
# Milter applications.
|
|
#
|
|
# This feature is available in Postfix 2.7 and later.
|
|
#
|
|
# FILTERS WHILE DELIVERING MAIL
|
|
# Postfix supports all four content inspection classes while
|
|
# delivering mail via SMTP.
|
|
#
|
|
# smtp_header_checks (default: empty)
|
|
#
|
|
# smtp_mime_header_checks (default: empty)
|
|
#
|
|
# smtp_nested_header_checks (default: empty)
|
|
#
|
|
# smtp_body_checks (default: empty)
|
|
# These features are available in Postfix 2.5 and
|
|
# later.
|
|
#
|
|
# COMPATIBILITY
|
|
# With Postfix version 2.2 and earlier specify "postmap -fq"
|
|
# to query a table that contains case sensitive patterns. By
|
|
# default, regexp: and pcre: patterns are case insensitive.
|
|
#
|
|
# TABLE FORMAT
|
|
# This document assumes that header and body_checks rules
|
|
# are specified in the form of Postfix regular expression
|
|
# lookup tables. Usually the best performance is obtained
|
|
# with pcre (Perl Compatible Regular Expression) tables. The
|
|
# regexp (POSIX regular expressions) tables are usually
|
|
# slower, but more widely available. Use the command "post-
|
|
# conf -m" to find out what lookup table types your Postfix
|
|
# system supports.
|
|
#
|
|
# The general format of Postfix regular expression tables is
|
|
# given below. For a discussion of specific pattern or
|
|
# flags syntax, see pcre_table(5) or regexp_table(5),
|
|
# respectively.
|
|
#
|
|
# /pattern/flags action
|
|
# When /pattern/ matches the input string, execute
|
|
# the corresponding action. See below for a list of
|
|
# possible actions.
|
|
#
|
|
# !/pattern/flags action
|
|
# When /pattern/ does not match the input string,
|
|
# execute the corresponding action.
|
|
#
|
|
# if /pattern/flags
|
|
#
|
|
# endif If the input string matches /pattern/, then match
|
|
# that input string against the patterns between if
|
|
# and endif. The if..endif can nest.
|
|
#
|
|
# Note: do not prepend whitespace to patterns inside
|
|
# if..endif.
|
|
#
|
|
# if !/pattern/flags
|
|
#
|
|
# endif If the input string does not match /pattern/, then
|
|
# match that input string against the patterns
|
|
# between if and endif. The if..endif can nest.
|
|
#
|
|
# blank lines and comments
|
|
# Empty lines and whitespace-only lines are ignored,
|
|
# as are lines whose first non-whitespace character
|
|
# is a `#'.
|
|
#
|
|
# multi-line text
|
|
# A pattern/action line starts with non-whitespace
|
|
# text. A line that starts with whitespace continues
|
|
# a logical line.
|
|
#
|
|
# TABLE SEARCH ORDER
|
|
# For each line of message input, the patterns are applied
|
|
# in the order as specified in the table. When a pattern is
|
|
# found that matches the input line, the corresponding
|
|
# action is executed and then the next input line is
|
|
# inspected.
|
|
#
|
|
# TEXT SUBSTITUTION
|
|
# Substitution of substrings from the matched expression
|
|
# into the action string is possible using the conventional
|
|
# Perl syntax ($1, $2, etc.). The macros in the result
|
|
# string may need to be written as ${n} or $(n) if they
|
|
# aren't followed by whitespace.
|
|
#
|
|
# Note: since negated patterns (those preceded by !) return
|
|
# a result when the expression does not match, substitutions
|
|
# are not available for negated patterns.
|
|
#
|
|
# ACTIONS
|
|
# Action names are case insensitive. They are shown in upper
|
|
# case for consistency with other Postfix documentation.
|
|
#
|
|
# BCC user@domain
|
|
# Add the specified address as a BCC recipient, and
|
|
# inspect the next input line. The address must have
|
|
# a local part and domain part. The number of BCC
|
|
# addresses that can be added is limited only by the
|
|
# amount of available storage space.
|
|
#
|
|
# Note 1: the BCC address is added as if it was spec-
|
|
# ified with NOTIFY=NONE. The sender will not be
|
|
# notified when the BCC address is undeliverable, as
|
|
# long as all down-stream software implements RFC
|
|
# 3461.
|
|
#
|
|
# Note 2: this ignores duplicate addresses (with the
|
|
# same delivery status notification options).
|
|
#
|
|
# This feature is available in Postfix 3.0 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# DISCARD optional text...
|
|
# Claim successful delivery and silently discard the
|
|
# message. Do not inspect the remainder of the input
|
|
# message. Log the optional text if specified, oth-
|
|
# erwise log a generic message.
|
|
#
|
|
# Note: this action disables further header or
|
|
# body_checks inspection of the current message and
|
|
# affects all recipients. To discard only one recip-
|
|
# ient without discarding the entire message, use the
|
|
# transport(5) table to direct mail to the discard(8)
|
|
# service.
|
|
#
|
|
# This feature is available in Postfix 2.0 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# DUNNO Pretend that the input line did not match any pat-
|
|
# tern, and inspect the next input line. This action
|
|
# can be used to shorten the table search.
|
|
#
|
|
# For backwards compatibility reasons, Postfix also
|
|
# accepts OK but it is (and always has been) treated
|
|
# as DUNNO.
|
|
#
|
|
# This feature is available in Postfix 2.1 and later.
|
|
#
|
|
# FILTER transport:destination
|
|
# Override the content_filter parameter setting, and
|
|
# inspect the next input line. After the message is
|
|
# queued, send the entire message through the speci-
|
|
# fied external content filter. The transport name
|
|
# specifies the first field of a mail delivery agent
|
|
# definition in master.cf; the syntax of the next-hop
|
|
# destination is described in the manual page of the
|
|
# corresponding delivery agent. More information
|
|
# about external content filters is in the Postfix
|
|
# FILTER_README file.
|
|
#
|
|
# Note 1: do not use $number regular expression sub-
|
|
# stitutions for transport or destination unless you
|
|
# know that the information has a trusted origin.
|
|
#
|
|
# Note 2: this action overrides the main.cf con-
|
|
# tent_filter setting, and affects all recipients of
|
|
# the message. In the case that multiple FILTER
|
|
# actions fire, only the last one is executed.
|
|
#
|
|
# Note 3: the purpose of the FILTER command is to
|
|
# override message routing. To override the recipi-
|
|
# ent's transport but not the next-hop destination,
|
|
# specify an empty filter destination (Postfix 2.7
|
|
# and later), or specify a transport:destination that
|
|
# delivers through a different Postfix instance
|
|
# (Postfix 2.6 and earlier). Other options are using
|
|
# the recipient-dependent transport_maps or the sen-
|
|
# der-dependent sender_dependent_default_transport-
|
|
# _maps features.
|
|
#
|
|
# This feature is available in Postfix 2.0 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# HOLD optional text...
|
|
# Arrange for the message to be placed on the hold
|
|
# queue, and inspect the next input line. The mes-
|
|
# sage remains on hold until someone either deletes
|
|
# it or releases it for delivery. Log the optional
|
|
# text if specified, otherwise log a generic message.
|
|
#
|
|
# Mail that is placed on hold can be examined with
|
|
# the postcat(1) command, and can be destroyed or
|
|
# released with the postsuper(1) command.
|
|
#
|
|
# Note: use "postsuper -r" to release mail that was
|
|
# kept on hold for a significant fraction of $maxi-
|
|
# mal_queue_lifetime or $bounce_queue_lifetime, or
|
|
# longer. Use "postsuper -H" only for mail that will
|
|
# not expire within a few delivery attempts.
|
|
#
|
|
# Note: this action affects all recipients of the
|
|
# message.
|
|
#
|
|
# This feature is available in Postfix 2.0 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# IGNORE Delete the current line from the input, and inspect
|
|
# the next input line. See STRIP for an alternative
|
|
# that logs the action.
|
|
#
|
|
# INFO optional text...
|
|
# Log an "info:" record with the optional text... (or
|
|
# log a generic text), and inspect the next input
|
|
# line. This action is useful for routine logging or
|
|
# for debugging.
|
|
#
|
|
# This feature is available in Postfix 2.8 and later.
|
|
#
|
|
# PASS optional text...
|
|
# Log a "pass:" record with the optional text... (or
|
|
# log a generic text), and turn off header, body, and
|
|
# Milter inspection for the remainder of this mes-
|
|
# sage.
|
|
#
|
|
# Note: this feature relies on trust in information
|
|
# that is easy to forge.
|
|
#
|
|
# This feature is available in Postfix 3.2 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# PREPEND text...
|
|
# Prepend one line with the specified text, and
|
|
# inspect the next input line.
|
|
#
|
|
# Notes:
|
|
#
|
|
# o The prepended text is output on a separate
|
|
# line, immediately before the input that
|
|
# triggered the PREPEND action.
|
|
#
|
|
# o The prepended text is not considered part of
|
|
# the input stream: it is not subject to
|
|
# header/body checks or address rewriting, and
|
|
# it does not affect the way that Postfix adds
|
|
# missing message headers.
|
|
#
|
|
# o When prepending text before a message header
|
|
# line, the prepended text must begin with a
|
|
# valid message header label.
|
|
#
|
|
# o This action cannot be used to prepend
|
|
# multi-line text.
|
|
#
|
|
# This feature is available in Postfix 2.1 and later.
|
|
#
|
|
# This feature is not supported with mil-
|
|
# ter_header_checks.
|
|
#
|
|
# REDIRECT user@domain
|
|
# Write a message redirection request to the queue
|
|
# file, and inspect the next input line. After the
|
|
# message is queued, it will be sent to the specified
|
|
# address instead of the intended recipient(s).
|
|
#
|
|
# Note: this action overrides the FILTER action, and
|
|
# affects all recipients of the message. If multiple
|
|
# REDIRECT actions fire, only the last one is exe-
|
|
# cuted.
|
|
#
|
|
# This feature is available in Postfix 2.1 and later.
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# REPLACE text...
|
|
# Replace the current line with the specified text,
|
|
# and inspect the next input line.
|
|
#
|
|
# This feature is available in Postfix 2.2 and later.
|
|
# The description below applies to Postfix 2.2.2 and
|
|
# later.
|
|
#
|
|
# Notes:
|
|
#
|
|
# o When replacing a message header line, the
|
|
# replacement text must begin with a valid
|
|
# header label.
|
|
#
|
|
# o The replaced text remains part of the input
|
|
# stream. Unlike the result from the PREPEND
|
|
# action, a replaced message header may be
|
|
# subject to address rewriting and may affect
|
|
# the way that Postfix adds missing message
|
|
# headers.
|
|
#
|
|
# REJECT optional text...
|
|
# Reject the entire message. Do not inspect the
|
|
# remainder of the input message. Reply with
|
|
# optional text... when the optional text is speci-
|
|
# fied, otherwise reply with a generic error message.
|
|
#
|
|
# Note: this action disables further header or
|
|
# body_checks inspection of the current message and
|
|
# affects all recipients.
|
|
#
|
|
# Postfix version 2.3 and later support enhanced sta-
|
|
# tus codes. When no code is specified at the begin-
|
|
# ning of optional text..., Postfix inserts a default
|
|
# enhanced status code of "5.7.1".
|
|
#
|
|
# This feature is not supported with smtp header/body
|
|
# checks.
|
|
#
|
|
# STRIP optional text...
|
|
# Log a "strip:" record with the optional text... (or
|
|
# log a generic text), delete the input line from the
|
|
# input, and inspect the next input line. See IGNORE
|
|
# for a silent alternative.
|
|
#
|
|
# This feature is available in Postfix 3.2 and later.
|
|
#
|
|
# WARN optional text...
|
|
# Log a "warning:" record with the optional text...
|
|
# (or log a generic text), and inspect the next input
|
|
# line. This action is useful for debugging and for
|
|
# testing a pattern before applying more drastic
|
|
# actions.
|
|
#
|
|
# BUGS
|
|
# Empty lines never match, because some map types mis-behave
|
|
# when given a zero-length search string. This limitation
|
|
# may be removed for regular expression tables in a future
|
|
# release.
|
|
#
|
|
# Many people overlook the main limitations of header and
|
|
# body_checks rules.
|
|
#
|
|
# o These rules operate on one logical message header
|
|
# or one body line at a time. A decision made for one
|
|
# line is not carried over to the next line.
|
|
#
|
|
# o If text in the message body is encoded (RFC 2045)
|
|
# then the rules need to be specified for the encoded
|
|
# form.
|
|
#
|
|
# o Likewise, when message headers are encoded (RFC
|
|
# 2047) then the rules need to be specified for the
|
|
# encoded form.
|
|
#
|
|
# Message headers added by the cleanup(8) daemon itself are
|
|
# excluded from inspection. Examples of such message headers
|
|
# are From:, To:, Message-ID:, Date:.
|
|
#
|
|
# Message headers deleted by the cleanup(8) daemon will be
|
|
# examined before they are deleted. Examples are: Bcc:, Con-
|
|
# tent-Length:, Return-Path:.
|
|
#
|
|
# CONFIGURATION PARAMETERS
|
|
# body_checks
|
|
# Lookup tables with content filter rules for message
|
|
# body lines. These filters see one physical line at
|
|
# a time, in chunks of at most $line_length_limit
|
|
# bytes.
|
|
#
|
|
# body_checks_size_limit
|
|
# The amount of content per message body segment
|
|
# (attachment) that is subjected to $body_checks fil-
|
|
# tering.
|
|
#
|
|
# header_checks
|
|
#
|
|
# mime_header_checks (default: $header_checks)
|
|
#
|
|
# nested_header_checks (default: $header_checks)
|
|
# Lookup tables with content filter rules for message
|
|
# header lines: respectively, these are applied to
|
|
# the initial message headers (not including MIME
|
|
# headers), to the MIME headers anywhere in the mes-
|
|
# sage, and to the initial headers of attached mes-
|
|
# sages.
|
|
#
|
|
# Note: these filters see one logical message header
|
|
# at a time, even when a message header spans multi-
|
|
# ple lines. Message headers that are longer than
|
|
# $header_size_limit characters are truncated.
|
|
#
|
|
# disable_mime_input_processing
|
|
# While receiving mail, give no special treatment to
|
|
# MIME related message headers; all text after the
|
|
# initial message headers is considered to be part of
|
|
# the message body. This means that header_checks is
|
|
# applied to all the initial message headers, and
|
|
# that body_checks is applied to the remainder of the
|
|
# message.
|
|
#
|
|
# Note: when used in this manner, body_checks will
|
|
# process a multi-line message header one line at a
|
|
# time.
|
|
#
|
|
# EXAMPLES
|
|
# Header pattern to block attachments with bad file name
|
|
# extensions. For convenience, the PCRE /x flag is speci-
|
|
# fied, so that there is no need to collapse the pattern
|
|
# into a single line of text. The purpose of the
|
|
# [[:xdigit:]] sub-expressions is to recognize Windows CLSID
|
|
# strings.
|
|
#
|
|
# /etc/postfix/main.cf:
|
|
# header_checks = pcre:/etc/postfix/header_checks.pcre
|
|
#
|
|
# /etc/postfix/header_checks.pcre:
|
|
# /^Content-(Disposition|Type).*name\s*=\s*"?([^;]*(\.|=2E)(
|
|
# ade|adp|asp|bas|bat|chm|cmd|com|cpl|crt|dll|exe|
|
|
# hlp|ht[at]|
|
|
# inf|ins|isp|jse?|lnk|md[betw]|ms[cipt]|nws|
|
|
# \{[[:xdigit:]]{8}(?:-[[:xdigit:]]{4}){3}-[[:xdigit:]]{12}\}|
|
|
# ops|pcd|pif|prf|reg|sc[frt]|sh[bsm]|swf|
|
|
# vb[esx]?|vxd|ws[cfh]))(\?=)?"?\s*(;|$)/x
|
|
# REJECT Attachment name "$2" may not end with ".$4"
|
|
#
|
|
# Body pattern to stop a specific HTML browser vulnerability
|
|
# exploit.
|
|
#
|
|
# /etc/postfix/main.cf:
|
|
# body_checks = regexp:/etc/postfix/body_checks
|
|
#
|
|
# /etc/postfix/body_checks:
|
|
# /^<iframe src=(3D)?cid:.* height=(3D)?0 width=(3D)?0>$/
|
|
# REJECT IFRAME vulnerability exploit
|
|
#
|
|
# SEE ALSO
|
|
# cleanup(8), canonicalize and enqueue Postfix message
|
|
# pcre_table(5), format of PCRE lookup tables
|
|
# regexp_table(5), format of POSIX regular expression tables
|
|
# postconf(1), Postfix configuration utility
|
|
# postmap(1), Postfix lookup table management
|
|
# postsuper(1), Postfix janitor
|
|
# postcat(1), show Postfix queue file contents
|
|
# RFC 2045, base64 and quoted-printable encoding rules
|
|
# RFC 2047, message header encoding for non-ASCII text
|
|
#
|
|
# README FILES
|
|
# Use "postconf readme_directory" or "postconf html_direc-
|
|
# tory" to locate this information.
|
|
# DATABASE_README, Postfix lookup table overview
|
|
# CONTENT_INSPECTION_README, Postfix content inspection overview
|
|
# BUILTIN_FILTER_README, Postfix built-in content inspection
|
|
# BACKSCATTER_README, blocking returned forged mail
|
|
#
|
|
# LICENSE
|
|
# The Secure Mailer license must be distributed with this
|
|
# software.
|
|
#
|
|
# AUTHOR(S)
|
|
# Wietse Venema
|
|
# IBM T.J. Watson Research
|
|
# P.O. Box 704
|
|
# Yorktown Heights, NY 10598, USA
|
|
#
|
|
# Wietse Venema
|
|
# Google, Inc.
|
|
# 111 8th Avenue
|
|
# New York, NY 10011, USA
|
|
#
|
|
# HEADER_CHECKS(5)
|